std::error_condition

class error_condition;

std::error_condition holds a platform-independent value identifying an error condition. Like std::error_code, it is uniquely identified by an integer value and a std::error_category, but unlike std::error_code, the value is not platform-dependent.

A typical implementation holds one integer data member (the value) and a pointer to an std::error_category.

Member functions

Non-member functions

Helper classes

Notes

The comparison between a std::error_code and a std::error_condition is defined by their error categories. Notably, an error condition of std::generic_category may compare equal to an error code of a specific category (e.g. std::system_category), if they represent the same kind of error.

A std::errc value can be compared to an error code via implicit conversion to std::error_condition.

#include <cerrno>
#include <iostream>
#include <system_error>
#include <Windows.h>

int main()
{
    std::error_code ec{ERROR_FILE_EXISTS, std::system_category()};
    std::error_condition econd{EEXIST, std::generic_category()};

    std::cout.setf(std::ios::boolalpha);
    std::cout << (ec == econd) << '\n'; // typically true
    std::cout << (ec == std::errc::file_exists) << '\n'; // ditto
    std::cout << (ec == make_error_code(std::errc::file_exists)) << '\n'; // false:
                                                                     // different category
}

true
true
false

See also